Why is this happening now?

Yellowstone National Park evacuated more than 10,000 visitors on Tuesday after flash floods ravaged the park. Roads and bridges were washed out, sewer lines ruptured, and communities at the park’s gates were cut off from roads. Yellowstone remains closed and the North Gateway likely won’t reopen this season.

Although scientists and land managers are surprised by the magnitude of the flooding, unprecedented in 100 years of recorded history, they recognize the similarities to the events predicted by their data. They just didn’t expect them to happen this year.

“As a scientist, I’d say it’s very much in line with what we might expect,” says Cathy Whitlock, paleoclimatologist and lead author of the Greater Yellowstone Climate Assessment, the first such report ever. on an ecosystem. “As a human being, I would say I’m shocked.”

While more research will be needed to confirm whether climate change has made this flooding more extreme, the 2021 Greater Yellowstone Climate Assessment predicts significant changes in precipitation, including when it will arrive and what form it will take. Scientists expect more rain in spring, less snow in winter. The assessment also predicts an increase in annual precipitation in Yellowstone National Park.

The changes are already documented in the assessment. Since 1950, spring precipitation in the region has increased by 17% in April and 23% in May. Snowfall has decreased even though overall annual precipitation has increased. This means rather than a slow release of meltwater in the valleys during the summer months, rainfall tends to combine with melting snow causing riskier events like the recent flood.

Climate change is shaping the landscape

Throughout its tumultuous geological history, climate change and extreme flooding have shaped the landscape around Yellowstone. Even today, changing natural events are a part of life in the western United States. For example, last year Yellowstone National Park received the lowest rainfall on record in June.

Ann Rodman, Geographic Information Systems Manager at Yellowstone National Park, who works on climate adaptation planning, thought that this summer would be similarly parched. Just two months ago, she calculated a 5% risk of flooding in the park. Then a big snowstorm hit the mountains on Memorial Day after an already cool and wet spring.

Still, she expected those moisture gains from the mountains to dry up once the warm months started.

In mid-June, the jet stream in unusually wet weather carried raindrops onto the exceptionally snow-capped mountains. The warm temperatures helped melt the snowpack. And as temperatures warm, these rain-on-snow events are expected to become more frequent at higher elevations in western North America, while a weaker snowpack will make them less frequent at lower elevations. .

Yellowstone Superintendent Cam Sholly told a press conference on Tuesday that he had been informed that the flooding could be a millennial event. One of the highest recorded flow measurements for the Yellowstone River was 31,000 cubic feet per second, recorded in the 1990s. Flow readings during the recent flood reached 51,000 cubic feet per second.

“What happened this week was not what I expected,” Rodman said. June precipitation this year is now more than 400 percent above average in parts of Montana and Wyoming that include Yellowstone. “We had rain all night and all day and it was pretty torrential. We just don’t get that kind of rain here. On Monday it watched from his home in Gardiner, just outside Yellowstone’s north entrance, as park staff quarters slid into the Yellowstone River.

Although the current floods are similar to what Rodman and others expect based on long-term climate forecasts, they are surprising in that earlier this month it was ready to tell people about a severe drought and a fire.

“We agree that we couldn’t have anticipated this,” Rodman said. “So what should we learn from this and what should we think about moving forward?”

Prepare for the worst

This growing need to expect rapidly changing conditions is why Yellowstone National Park and the National Park Service are considering planning for different scenarios as the climate changes. Bruce Stein, chief scientist for the National Wildlife Federation, collaborated with the Park Service on a 2021 climate planning report. He says that compared to other federal agencies, the organization is “ahead of the curve.”

But he too was caught off guard. Several years ago, when he trained Yellowstone National Park staff in climate planning, they focused on features that draw visitors to Yellowstone, such as bison and wolves. Roads, bridges and washed away houses were not on their radar.

“Even when we try to do our best to project the range of things possible, we end up being surprised,” Stein says. “And I think the flooding in Yellowstone falls into that category.”

“It’s these unexpected and often worse than projected worst-case scenarios that we’re starting to see.”

Thanks to recent flooding, Yellowstone National Park and small towns in southwestern Montana will join the ranks of communities that are forced to redesign their infrastructure or likely end up rebuilding it after the next flood.

“It’s really clear that our infrastructure is not well positioned for climate change,” says Whitlock. “The fact that we are losing these roads, having these huge landslides and houses being washed away clearly means that we are not thinking enough about the impacts of climate change on our land use and infrastructure development. . And we need to do a better job of that. Because that’s the cost and that’s the tragedy.

The road ahead

Yellowstone National Park is already taking inspiration from climate planning thinking about the now-washed-out North Entrance Road that carried visitors the five miles from the park’s popular North Entrance at Gardiner to its headquarters at Mammoth Hot Springs. The park superintendent told the press conference that the road will not be rebuilt in the same place, citing changes on the horizon.

“I think it’s smart and forward-looking,” Rodman says. “[The superintendent] is very aware of the need to consider the potential impacts of climate change when planning infrastructure projects. I think the recent event underscored just how significant those impacts can be.

Similarly, Denali National Park in Alaska is battling road closures caused by melting permafrost and exploring alternatives to road repairs, including a bridge over the landslide or road rerouting.

As climate planners, Rodman and his colleagues struggle with these issues daily. “It affects everything, so how do you get it done in a thoughtful way with limited resources? What’s the most effective thing you can do that will actually make a difference?”

For the millions of people who love National Parks and Yellowstone, and for those who live in the area, or whose summer plans have been shattered, unprecedented events can come with a kind of heartbreak, even resentment.

Stein suggests audiences try to embrace the unexpected, even though it can be heartbreaking and difficult to watch our favorite places quickly and sometimes drastically reshaped.

“I think on a deeper level, to understand and love the concept of what a national nature park is is to accept that there are changes that have always taken place,” he says.

“And, of course, now they are happening on an accelerated scale. What makes it difficult is that so many of these accelerated changes are due to climate impacts that have a human imprint on them.

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